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5000t heavy lift mast crane pedestal supports frame

11 adjustable roller boxes Removable stinger handling guide the pipe frame supports section 1

Stinger Section 2

Stinger Section 1

The Stinger has a maximum length of 92.5m

Stinger Section 3

escalator. The main function of the escalator is to hold the double joint in pincer clamps and raise it from the main deck, up over curved rails, to the base of the pipe tower. The erector then takes the horizontal pipe and raises it to the vertical where it is swung into the J lay tower. “A feature of the J lay tower is its ability to change angle to suit the pipelaying operation,” said Gilbert. “This means that the vessel heading can be optimised for prevailing conditions independent of the ship’s heading.” The tower can tilt at an angle of up to 15 deg via a gimbal at its mid-point which also allows the entire tower to azimuth 0 deg to 180 deg.

The mast is able to move 15deg from vertical in every direction

Erector moves double joints into the J lay tower Crane

This means that the erector has to work at various angles, and that the escalator must be flexible enough to feed the erector with the double joints at the correct angle.

The pipelay is typically supported by remotely operated vehicles (ROV). The Seven Borealis uses two 3000m rated Schilling ACV units. They incorporate a range of subsea equipment including a suite of Kongsberg SIT and colour/ monochrome zoom cameras as well as a Tritech Super Sea King sonar, Kongsberg transponder, a CDL ring laser gyro and RDI Doppler velocity log. One historical challenge with launching ROVs is getting them through the wave zone. Many previous Subsea 7 ROVs deployed by a cursor system to physically submerge the vehicle. The Seven Borealis designers, however, selected a pair of MacArtney MASH 3400 MK1 active heave compensation winch to minimise the movement caused by waves.

In the tower, the pipe is held in place by friction clamps, although collars can also be used. These pipes can hold 750t of pipe. They move the pipe using a ‘hand-over-hand’ action. The J-lay tower incorporates two stations that work simultaneously. The first is for welding and inspection. Instead of the automatic welding tool revolving around the pipe, this system has a novel rotating floor. “The floor remains horizontal, even if the J lay tower is at an angle,” said Terence Vehmeijer. “This allows the welder to work around the pipe while standing still . This improves ergonomics and weld quality. “Furthermore, the rotating floor can a slide up and down the pipe to allow welds at two different heights. This is important for pipe in pipe welding.” Escalator moves double joints from the main deck to erector

J-lay tower

UT2 August 2012

The second variable workstation is set to be exactly one pipelength from the first station so the two can work simultaneously. It is predominantly used for field joint coating as well as weld inspection.


Whip hoist

Main hoist Auxiliary hoist

UT3 August 2012  

The August edition of UT3, the magazine of the SUT

UT3 August 2012  

The August edition of UT3, the magazine of the SUT